1. Field of the Invention
The present invention relates to methods and apparatus for setting and unsetting an inflatable packer or bridge plug in a subterranean oil or gas well by using coiled tubing or remedial tubing for pumping fluids to the packer or bridge plug. More particularly, the invention relates to improved methods and apparatus for utilizing an inflatable packer for treatment, cementing or flow control operations on a producing well or an injection well without requiring the removal of the primary tubing string from the well, or killing of the well.
2. Description of the Prior Art
Those skilled in the art relating to remedial operations associated with the production and treatment of subterranean oil and gas wells have long utilized threaded or coupled remedial tubing inserted through production tubing for pumping fluids from the surface to one or more inflatable packers disposed downhole adjacent production formations. More recently, continuous coiled tubing has generally replaced threaded or coupled tubing in such applications, since coiled tubing may be more rapidly inserted into the well and may be easily passed through production tubing and related downhole equipment because its diameter is consistently the same size.
Typical remedial coiled tubing apparatus is described in the 1973 Composite Catalogue of Oil Field Equipment and Services, at page 662 (GULF PUBLISHING CO., Houston, Tex.), and manufactured by Bowen Tools, Inc. of Houston, Tex. Apparatus relating to the coiled tubing technique is more particularly described in U.S. Pat. Nos: 3,182,877 and 3,614,019. The need frequently arises in remedial or stimulation operations to pass an inflatable packer or bridge plug through small diameter restrictions, e.g. three and a half inch tubing string, and set the packer or bridge plug in a relatively large diameter casing, e.g., seven inch casing, to accomplish remedial or stimulation operations. The packer or bridge plug is then deflated and retrieved to the surface through the tubing string. Recent advances, such as those disclosed in U.S. Pat. No. 4,349,204, enable inflatable packers or bridge plugs to pass through such relatively small diameter tubing string, effectively seal with a larger diameter casing, and then be retrievable to the surface through the tubing string.
The above referred to co-pending applications, each of which is hereby incorporated by reference in this application, deal with the problem of effecting a fluid pressure actuated disconnection of the coiled tubing from the inflatable packer or bridge plug. The tensile strength of such coiled tubing is very small and, during the retrieval of the inflatable packer or bridge plug, a hang-up can occur which cannot be dislodged by tensile forces exerted on the coiled tubing. It is of course understood that rotation of the coiled tubing is a practical impossibility. To solve this problem, the first filed of the above identified copending applications, discloses a fluid pressure actuated disconnecting mechanism for incorporation in a run-in tool which is conventionally secured to the bottom end of coiled tubing by set screws, or any other conventional means, and is detachably engagable with the top end of an inflatable packer by a fluid pressure actuated release mechanism. The application of a fluid pressure through the coiled tubing to the fluid pressure actuated release mechanism at a predetermined pressure level effects the release of the run-in tool from the inflatable packer, permitting the coiled tubing to be removed and subsequent operations on the inflatable packer performed by wireline.
Additionally, in the first filed application, Ser. No. 877,421, the fluid pressure to effect the inflation of a packer is derived by dropping or pumping a ball through the coiled tubing which seats on a valve seat sleeve which is shearably secured in the bore of an inflatable packer. After inflation of the inflatable element of the inflatable packer has been accomplished, an increase in fluid pressure supplied by the coiled tubing will effect the shearing of the securement of the ball seat sleeve and permit the ball and the seat sleeve to be forced downwardly out of the packer bore, thus opening the bore of the packer so that treatment fluid can be supplied through the coiled tubing to the isolated portion of the well below the packer. When the treatment operation is completed, and it is desired to remove the inflatable packer from the well, a second ball is dropped or pumped which engages a second valve seat sleeve shearably secured in the bore of the inflatable packer. The valve seat sleeve cooperates with two axially spaced seals to effect a bridging connection across radial ports provided in the wall of the tubular packer. Thus, an increase in fluid pressure applied to the second ball valve will effect the downward movement of the second ball valve seat and will open the radial ports to equalize the fluid pressures above and below the inflatable element of the inflatable packer.
A third, still larger ball valve seat is provided in the upper portions of the inflatable packer to receive a third ball and this ball permits the fluid pressure applied through the coiled tubing to be increased to a level which will effect the disengagement of the fluid pressure actuated release mechanism carried by the run-in tool. Normally, the fluid pressure actuated release mechanism is not employed unless an obstruction is encountered during retrieval of the inflatable packer.
The disclosure of the above referred to co-pending application, Ser. No. 113,172, filed 10/23/87 differs from that of the first filed copending application in that inflatable bottom is a bridge plug and the bottom end of the inflatable tool mounts an axially shiftable plug valve having a sleeve portion which is normally positioned to permit circulation of fluid through ports in the wall of such sleeve portion during run-in. The sleeve valve incorporates a ball seating surface and the first mentioned ball is dropped to seat on such surface. The application of fluid pressure through the coiled tubing effects an axial shifting of the cylindrical valve plug to close the circulation ports after run-in.
Experimentation with the inflatable packer or bridge plug mechanisms described in the first two of the above referred to co-pending applications has revealed many potential applications for such mechanisms. At the same time, some applications involve the disconnection of the coiled tubing from the inflatable packer and the retrieval of the coiled tubing from the well while the inflatable packer or bridge plug remains in an inflated, set condition in the well. Under these circumstances, it is necessary to provide an alternate mechanism for effecting the fluid pressure equalization above and below the inflated element of the inflatable packer prior or bridge plug to effecting the deflation of such inflated tool. The incorporation of a wireline operated pressure equalization mandrel in the inflatable tool is disclosed in the third co-pending application, Ser. No. 112,888 filed 10/23/87.
Other applications of the inflatable packer mechanism described in the above referred to co-pending applications have required that the bore of the inflatable packer remain free of any ball or valve obstruction after the coiled tubing is disconnected from the inflated packer. Still other applications require the incorporation of a plurality of axially spaced, inflatable packing elements on a single packer or bridge plug.